Wipe the chicken joints. Cut the onions in slices, and the potatoes in medium-thick slices. Brown the chicken pieces in half the butter. In a casserole, put a thick layer of potatoes, then onions and chicken pieces. Season well with salt and pepper and add small pieces of butter. Put on another layer of potatoes, then onions, chicken and finally potatoes.
Season again and pour on the stock. Put on a piece of buttered paper and a lid. Cook at 300°F, 150°C, gas mark 2 for two and a half hours, adding a little more stock or water if needed. If an iron casserole is used, this dish may be simmered gently on a low heat on top of the stove. Sprinkle with parsley before serving.